Method for manufacturing a flanged element and a flanged element

ABSTRACT

A flanged member for a pipe system, and a method of manufacturing same. The flanged member has a radially projecting flange part and a pipe part. The flange part has a front end surface connects to another flange part, and a radially planar rear end surface facing the pipe part which delimits the rear end of the flange part against the pipe part, together with a radially inward extension of the rear end surface. The pipe part has a free end, adapted to be welded into the pipe system. Before final machining of the front surface of the flange part, the pipe part has an axial length such that its mass is at least 35% of the mass of the flange part so that upon welding of the free end of the pipe part, there is substantially no distortion of the rear surface of the flange part.

BACKGROUND OF THE INVENTION

The present invention relates to a method for the manufacture of aflanged member for a pipe system and to a flanged member intended foruse in a pipe system.

It has been known for a long time to join various parts and componentsfor pressure equipment, especially in pipe systems, by using flangedmembers, usually called flanged pipe joints. By flanged member, alsonamed flange member or merely flange, is here intended a pipe elementhaving a ring-shaped collar or flange at one of its ends. So-calledflanged pipe joints include two flanged members that are boltedtogether, and they are used, for instance, for the joining of pipes innumerous applications. A flanged member is then attached to one end of apipe, usually by welding. Also an opposite piece of pipe is providedwith a flanged member, and the flanged pipe joint is achieved by boltingthose two flanged members together. Flanged members are also used forthe connection of a piece of pipe to different components included in apipe system, as for instance valves, a Y-piece or just another piece ofpipe. In such a case a flanged member is attached to the free end of thepipe and then bolted to a corresponding and for this purpose adaptedpart of the valve. Also, other types of joint arrangements may be used,for instance joints of clamp or hoop type.

Flanged joints and other joints, where flanged members are incorporated,are used in numerous applications. It follows, that the actualdimensions of these pipes and flanged members may vary substantially.Regarding large size pipe, as for an example with applications withinthe offshore-, subsea-, process- and petroleum-industries and also innuclear power plants, flanged joints and flanged members of traditionaldesign, are characterised by considerable weight, large bulk and highcost. However, a special type of flanged joint/flanged member is known,a so called compact flange system, in which certain dimensioningprinciples are applied such that the flanges can be made substantiallysmaller than by using conventional design. The invention in the presentcase is particularly well suited for this type of compact flanges,although it is not limited to such.

As the flanged member normally is very bulky and consequently is a muchmore expensive component than a straight piece of pipe, an effort isusually made to make the flanged member as short as possible, in orderto limit the need for space and the cost of material. In practice thismeans that its non-flanged end is made as short as possible. In caseswith pipes having a relatively large outside diameter and consequently alarge flange diameter, and at the same time a comparatively smallwall-thickness, it will occur, during welding of the non-flanged end ofthe flanged member to a pipe element in the pipe system, such high heattransfer in the flanged member that the contact surface of the flangedend of the flanged member becomes deformed and warped. This problem isalso common with small size flanges, having a rather small mass relativeto the pipe shaped part of the flange member, and which therefore heatup rapidly. It is readily understood, that this circumstance does impairthe performance of the joint tightness, which in many applicationscreates a most serious problem. Even a defect in the tightness thatresults in a very small leakage may, for instance, create a seriousperil in cases when substances, which may endanger the environment, aretransported in the pipe system.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to offer a solutionto the above described problems. This is achieved by adjusting therespective masses of the pipe part and the flange part so that the massof the pipe part is equal to at least 35% of the mass of the flangepart, particularly 40% to 200% and more particularly 40% to 100% of themass of the flange part as well as to a flanged member with thoserelative masses.

According to the present invention, a method for the manufacture of aflanged member for a pipe system is proposed, said flanged membercomprising a radially projecting flange, forming a flange part, andfurther comprising a pipe part, said flange part having a front endsurface adapted to be assembled with another element in the pipe system,and a rear end surface facing said pipe part, said rear end surface ofthe flange part being essentially plane in a radial direction anddelimiting the flanged part at its rear end against the pipe parttogether with an extension of said rear end surface inwards, in theradial direction, and said pipe part having a free end adapted to beassembled with the pipe system, furthermore said flange part having amass M_(f) and said pipe part having a mass M_(p), characterised inthat, before the final machining of the front end surface of said flangepart, the pipe part is given such a length (a) in the axial directionthat its mass M_(p) is equal to at least 35% of the mass M_(f) of theflange part.

In practice, this means that the pipe part of the flanged member is madesubstantially longer than what is the standard practice, which leads tothe advantageous result that, when the extended end of the pipe part isbeing welded to the pipe system, the heat transfer that results from thewelding will not cause any substantial deformation of the contactsurface of the flange. Thus, due to the extended pipe part, asubstantial part, if not all, of the heat generated will be absorbed bythe extended pipe part, such that the heat transferred to the endsurface of the flange becomes drastically reduced. Another advantageouseffect of the extended pipe part is that it will have a stiffeningeffect on the structure, which also contributes to considerablereduction of the peril of deforming of the end surface of the flange.

Regarding the length of the pipe part, this is adapted on a case to casebasis, and there is not necessarily any upper limit, based on technicalconsiderations, but in many cases it is guided by practicalcircumstances, for instance what space is available and such.Advantageously, the length (a) of the pipe part in the axial directionmay be made long enough for its mass M_(p) to be between 40% and 200% ofthe mass M_(f) of the flange part. Preferably, the length (a) of thepipe part in the axial direction is such that its mass M_(p) is between40% and 100% of the mass M_(f) of the flange part.

According to an advantageous embodiment, the entire pipe part is made inone piece with the other part(s) of the flanged member. In most casesthis is the most practical way, if you already know beforehand that theflanged member will be exposed to heat transfer.

According to another advantageous embodiment, at least part of the pipepart is manufactured as a separate part, which is attached to the restof the flanged member before final machining of the front end surface ofthe flange part. This has the advantage of ensuring flexibility in themanufacture. The separate extension part can be joined to the flangedmember by welding, for example, which in itself may be expected toresult in deformation of the contact surface. By making such anextension, according to the above invention, before the final machiningof the contact surface of the flange end, i.e. the end surface, anypossible deformation of the contact surface will become corrected duringthe final machining operation, which also offers a substantial benefit.

The object of the present invention is also achieved by means of aflanged member manufactured according to the inventive method.

The inside diameters of flanged members and of attached pipes arepresumed to be essentially constant.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will now be described in more detail withreference being made to the attached drawing, FIG. 1, and its schematicillustration of one embodiment, which is to be regarded only as anon-limiting example:

FIG. 1 shows schematically a flanged member, in an axial cross-section,in accordance with the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

The flanged member 1, illustrated in FIG. 1, displays one end providedwith a flange 3 or ring-shaped collar, and forming a flange part 2, anda non-flanged end 5 forming a pipe part 4. The flange part 2 has a frontend surface or contact surface 7, intended for abutting against acorresponding surface of a pipe element, of a similar flanged member, orof some other type of component constituting a part of a pipe system.The flange part 2 also has a rear end surface 6 that is essentiallyplane and, in the illustrated case, principally at a right anglerelative to the centre axis of symmetry of the flanged member. Theflange 3 has through-bores 8 such that at assembly, the flanged memberis bolted together with another flanged member or component, by means ofbolts inserted in said bores. Normally there are a number of bores,equally spaced around the flange. All the way through the centre of theflanged member, there is a cylindrical duct 10.

The flanged member is normally connected to the pipe system, in which itis to become a part, by welding the non-flanged end 5 to the pipesystem. In accordance with the solution proposed by the presentinvention, the non-flanged end 5 shall be located such a long distancefrom the delicate front contact surface 7, that the flange part 2 is notaffected by any heating resulting from the welding, or at least is notaffected to such a degree that the front contact surface is affected inits turn, and becomes warped or affected in any other negative way. Thetransfer of heat, taking place between the pipe part and the flangepart, primarily is a function of their respective masses. For thispurpose, the flanged part 2 is regarded as delimited against the pipepart 4 by a plane 9, which is formed by the extension inwards, inessentially the radial direction, of the plane that is formed by therear end surface 6 of the flanged part. It follows, that the mass M_(f)of the flange part 2 may be calculated as being the mass in front of orto the left of the line/plane 9 in FIG. 1, while the mass M_(p) of thepipe part may be calculated as being the mass behind or to the right ofthe line/plane 9 in FIG. 1. Based on analysis and experiments supportingthe present invention, it has been concluded that the pipe part shallhave a length (a), as measured from the rear end surface 6 of the flangepart to the end 5 of the pipe part, being long enough for its mass M_(p)to be equal to at least 35% of the mass M_(f) of the flange part.

Since it occurs that cylindrical pipe extensions are welded to a flangedmember that has already been finally machined, its front end surface 7then risking deformation due to the influx of heat, it is very importantthat the pipe part has been given the concerned proper length (a) beforeany final machining of the flanged member and, in particular, of itsfront end surface 7.

The pipe part 4 may be given the concerned length (a) directly atmanufacture, or by the joining of an extension to the non-flanged endbefore the final machining operation.

In the embodiment illustrated in FIG. 1, there is an extension in theform of a separate part 15, provided in accordance with the presentinvention. The purpose of the extension 15 also is to increase therigidity of the entire flanged member, which also contributes in apositive manner to prevent deformation of the end surface 7 of theflange part 2, when the flanged member is being joined to a pipe systemby welding. It is understood that an extension made in one piece withthe flanged member does have the same function.

In FIG. 1, the transit-zone 12 between the flange and the non-flangedend is illustrated as a zone having an elliptic form, which is alreadyknown per se. It deserves being noted, that the rear end surface 6 ofthe flanged member does not necessarily need to be at a right anglerelative to the axial direction of the flanged member, but the rear endsurface may alternatively be slightly inclined, which is also known perse.

The present invention shall not be considered as being limited to theillustrated embodiment, given as an example only, but may be varied andmodified in numerous ways, as is readily understood by the personskilled in the art, within the scope of the appended patent claims.

1. A method for manufacture of a flanged member for a pipe systemincluded in pressure equipment, the flanged member including a radiallyprojecting flange part and a pipe part, the flange part having a frontface and a rear face and the pipe part having a first end and a free endlocated opposite the first end, the front face having a contact surfaceoperable to be assembled with a first part of the pipe system, the rearface of the flange part extending radially inwardly and merging with thefirst end of the pipe part delimiting the flange part at its rear end,the free end of the pipe part being operable to be welded to a secondpart of the pipe system, and the flange part having a mass M_(f) and thepipe part having a mass M_(p), the method comprising the steps of:machining the flanged member; and prior to final machining of the frontface of the flange part, restricting the pipe part to an axial length(a) selected such that the mass M_(p) of the pipe part is equal to atleast 35% of the mass M_(f) of the flange part so as to substantiallyeliminate distortion of the contact surface on the front face of theflange part upon welding of the free end of the pipe part.
 2. A methodaccording to claim 1, wherein the axial length (a) is selected such thatthe mass M_(p) of the pipe part is between 40% and 200% of the massM_(f) of the flange part.
 3. A method according to claim 1, wherein theaxial length (a) is selected such that the mass M_(p) of the pipe partis between 40% and 100% of the mass M_(f) of the flange part.
 4. Amethod according to claim 1, further comprising forming the pipe part inone piece with the rest of the flanged member.
 5. A method according toclaim 1, wherein at least a portion of the pipe part is made as aseparate part, which is attached to the rest of the flanged memberbefore the final machining of the front face of the flange part.
 6. Amethod for manufacture of a flanged member for a pipe system included inpressure equipment the flanged member including a radially projectingflange part and a pipe part, the flange part having a front face and arear face and the pipe part having a first end and a free end locatedopposite the first end, the front face having a contact surface operableto be assembled with a first part of the pipe system, the rear face ofthe flange part extending radially inwardly and merging with the firstend of the pipe part delimiting the flange part at its rear end, thefree end of the pipe part being operable to be welded to a second partof the pipe system, and the flange part having a mass M_(f) and the pipepart having a mass M_(p), the method comprising the steps of: machiningthe flanged member such that the pipe part includes a portion having asubstantially constant outer diameter and a predominantly ellipticaltransit zone extending from the rear face of the flange part to thesubstantially constant diameter portion of the pipe part; providing theflange part with a plurality of through-bores extending from the rearface to the front face; and prior to final machining of the front faceof the flange part, restricting the pipe part to an axial length (a)selected such the mass M_(p) of the pipe part is equal to at least 35%of the mass M_(f) of the flange part so as to substantially eliminatedistortion of the contact surface on the front face of the flange partupon welding of the free end of the pipe part.
 7. A flanged member foruse in a pipe system included in pressure equipment, the flanged membercomprising: a flange part having a mass M_(f), a front end with a frontface and a rear end with a rear face, the front face forming a contactsurface operable to be assembled with a first part of the pipe system,the rear face extending radially inwardly; and a pipe part having a massM_(p), a first end and a free end located opposite the first end, thefirst end of the pipe part merging with the rear face of the flange partdelimiting the rear end of the flange part, the free end being operableto be welded to a second part of the pipe system, wherein before finalmachining of the front face of the flange part, the pipe part has anaxial length (a) selected such that the mass M_(p) of the pipe part isequal to at least 35% of the mass M_(f) of the flange part so as tosubstantially eliminate distortion of the front face of the flange partupon welding of the free end of the pipe part.
 8. A flanged memberaccording to claim 7, wherein the axial length (a) of the pipe part isselected such that the mass M_(p) is between 40% and 200% of the massM_(f) of the flange part.
 9. A flanged member according to claim 8,wherein the axial length (a) of the pipe part is selected such that themass M_(p) is between 40% and 100% of the mass M_(f) of the flange part.10. A flanged member according to claim 7, wherein the entire pipe partis made in one piece together with the rest of the flanged member.
 11. Aflanged member according to claim 7, wherein at least a part of the pipepart is a separate part, which is attached to the rest of the flangedmember prior to final machining of said front face of the flange part.12. A flanged member according to claim 7, wherein the pipe partcomprises a portion having a substantially constant outer diameter and apredominantly elliptical transit zone located between the flange partand the portion of the pipe part that has the substantially constantouter diameter.
 13. A flanged member according to claim 12, furthercomprising a plurality of through-bores extending from the rear face ofthe flange part to the front face thereof.
 14. A flanged memberaccording to claim 12, wherein the rear face of the flange part issubstantially planar, and substantially parallel to the front face. 15.A flanged member according to claim 7 which is one half of a flangedpipe joint.
 16. A flanged member according to claim 7, furthercomprising a plurality of through-bores extending from the rear face ofthe flange part to the front face thereof.
 17. A flanged memberaccording to claim 7, wherein the contact surface forms a seal with acomplementary element of the first part of the pipe system, without anintermediate seal.